Process liquid chromatography (PLC) is increasingly being used in the chemical industries to extend the analysis capabilities of process gas chromatography (PGC). In many respects, PLC can be considered as a complement to PGC. There is considerable overlap between the two chromatographic techniques since many compounds can either be vaporized or dissolved. Many PLC analyses are involved with complex separations involving compounds that are difficult or impossible to separate by PGC. These include analyses of compounds that are non-volatile, thermally unstable, high boiling and which require excessive temperatures to vaporize, or which polymerize or react on heating.
One analysis of potential commercial importance is that of the mixture of 1,3-butadiene, styrene and cyclohexane. Such an analysis would be of some importance in the monitoring of operations in SBR rubber production. However, this analysis has been difficult to carry out in the past by gas chromatography due to the tendency of the styrene to polymerize on the column. This analysis has also been difficult to carry out by liquid chromatography due to incomplete separation of the 1,3-butadiene and the cyclohexane.